Two Quotations

Here are two quotes. The first is from Trouet et al 2009:

The increased pressure difference between the Azores High (+3 hPa) and the Icelandic Low (–5 hPa) during positive NAO phases results in enhanced zonal flow, with stronger westerlies transporting warm air to the European continent. The axis of maximum moisture transport and the preferred stormtrack extend further to the north and east during positive NAO phases when the Azores High is strengthened, resulting in wetter winters over northwestern Europe (50-to-200–mm positive anomalies per season) and decreased precipitation over southern Europe and northwestern Africa (50-to-100–mm negative anomalies per season).

The next quotation is not:

Judged by the implied shift of the upper westerlies, the main depression tracks and the zone of low pressure associated with them (the “Iceland low”) should have had, in the period 1000-1300, an average position 1-3 ° north of the modern normal (1900-1939 average) position– a displacement that probably implies less ice on the Arctic seas, because a northward progression by almost this amount between 1800 and 1940 went hand in hand with a roughly equal retreat of the ice…

The [MCA] appears as one of dry summers, i.e., an oceanic, summer anticyclonic type of regime. In the subsequent cold epoch,… the summers have contributed a more than proportionate share of the year’s rain, whereas the winters became relatively dry.

The exercise for today is 1) to identify the source of the second quotation [PLEASE DO NOT GOOGLE as anyone can google things and you immediately encounter a PPT that reveals the source] and 2) explain exactly how the Trouet et al 2009 explanation overturns (or even differs) from the explanation in the other article.

Yep, that wasn’t too hard. If you google it, you get my Heartland presentation. I’m embarrassed to say that, even though I prepared the Heartland talk only a month ago, it had slipped my mind, as the context was different.

If one parses the Lamb article, while he doesn’t use the term “North Atlantic Oscillation”, Lamb pays very close attention in this and other articles to changes in wind circulation and attributed the “Medieval Climatic Anomaly” to this explanation. Lamb 1965 commences with a lengthy such exposition and his references (Lamb and Johnson 1961, say) are just as extensive

I have H.H. Lamb’s book on climate change and there is a LOT of stuff in there that points in a direction completely opposite to any conclusions related to global warming. I have just had reason to re-read a lot of his work and while Lamb does talk about the warming in Greenland to Northern Europe being regional while the far east was cooler than normal, Lamb also ignored the data from the American Southwest that also showed warming during the MWP. So if it is regional warmth, it was one hell of a region.

Dennis, I’m as familiar as anyone with the proxy data. For the purposes of threaded blog discussion, it is my editorial opinion that it’s more fruitful to examine the narrower issue of whether there is a relevant difference between the “new” dynamical theory advocated in Trouet et al and Lamb’s theory. This requires readers to cross-read both articles and transliterate the somewhat different vocabulary – as Lamb does not use the term North Atlantic OScillation but does use Azores High and Iceland Low.

I’d be far more interested in a critic explaining the relevant difference than in people piling on.

I would have thought the former would melt ice, while greater precipitation might mean greater snowfall in Arctic climes.
Lamb (1965) ties into historic evidence:

“because a northward progression by almost this amount between 1800 and 1940 went hand in hand with a roughly equal retreat of the ice…”

suggesting the warmth dominated. (Though I have seen articles attributing Arctic melting to ocean currents or winds.)

Lamb (1965) quantifies:

“an average position 1-3 ° north of the modern normal (1900-1939 average) position– a displacement that probably implies less ice on the Arctic seas, because a northward progression by almost this amount between 1800 and 1940 went hand in hand with a roughly equal retreat of the ice…”

Trouet(2009) handwaves in the same direction:

“the preferred stormtrack extend further to the north and east”;

Steve: these latter quotes are the ones that I used in my thread. What’s been added here by reiterating them?

Presenting two paragraphs is not a particularly useful way of doing this.

I wasn’t trying to answer the question. Quite frankly, I have no idea what their answer would be. I think that two paragraphs are sufficient to pose the question.

Why does it have to?

As I understand it, academic articles are supposed to cite relevant literature. If Lamb 1965 contains a related theory using slightly different language, then I think that you should refer to it. They cite Lamb 1965 in another context (the prank part of their article) and thus they are aware of the Lamb article.